Avid's internal "canonical" ordering is Film (LF, CF, RF, LS, RS, Lfe). If you correctly import any 5.1 (SMPTE or Film), Avid will re-order the channels so that it has them in Film order. (You can discern that order by breaking up the 5.1 into Mono from the Track menu.) This is why when you import SMPTE, in the Import Settings dialog, Avid gives you the following info: "Multichannel Audio: 5.1 Surround: A1A3A2A5A6A4". It is telling you how it will re-order you tracks (in order to achieve Film order). When you imprt Film, there is no re-ordering.
Hence, a reliable way of figuring the track order of any arbitrary 5.1 audio file is to import it into Avid as Film, explode it to Mono, and then listen to each channel solo.